The present invention relates to a device for heating the washing liquid of a windshield wiper system, in particular a windshield washing system of a motor vehicle having a heating device.
Such devices are frequently employed in modern motor vehicles and are thus known. The device serves for heating the washing liquid. This is necessary since, in the event of low ambient temperatures, the washing liquid of the windshield wiper system tends to freeze even when antifreeze agents are present in the washing liquid. In one device known in actual practice, the heating means is developed as a counter-flow heat exchanger and is arranged in a washing-liquid line leading from a storage container to a washing nozzle. The counter-flow heat exchanger is used in a connecting thread of an oil drainage screw of an internal combustion engine of the motor vehicle and is heated by the motor oil of the internal combustion engine. The apparatus thus operates in a manner similar to a continuous flow heater and requires large heat transfer surfaces for the rapid transfer of the heat.
The known apparatus has the disadvantage that, despite large heat transfer surfaces, the heat exchanger is very slow. This has the result that, in the event of particularly low outside temperatures, an amount of washing liquid sufficient for cleaning of the windshield is available only after a long period of operation of the internal combustion engine. In order to obtain the smallest possible temperature difference between the motor oil and the washing liquid, it is furthermore necessary to make the heat transfer surfaces particularly large. The apparatus, however, is particularly large as a result of this.